Lights Flicker on different circuit

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  #1  
Old 05-07-04, 09:33 AM
Georgeb
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Lights Flicker on different circuit

I have a sump pump on it's own 15amp circuit with no other loads. When the pump kicks on it dims most of the lights in the house. I know the pump takes a decent amount of juice, but why would it dim lights that are on a completely different circuit? Would changing the breaker to a 20amp and upgrading the wiring to 12gage fix this problem?
 
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  #2  
Old 05-07-04, 10:17 AM
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Putting the sump pump on a larger circuit will make essentially no difference.

If lights on _different_ circuits are getting _dimmer_, then this indicates a problem with the main supply to your house. If they only get a little bit dimmer, then this might simply be normal voltage drop under load. If they get significantly dimmer, then this could indicate a bad connection in one of your supply hots, either in your panel, or at the utility drop. This should get checked by an electrician soon.

A bad connection means one thing: high resistance and _heat_. This can damage conductors or contacts, which would require you to replace the conductors or your panel. In extreme cases, a bad connection can produce enough heat to start a fire.

If any lights on different circuits are getting _brighter_, then this indicates a problem with your supply neutral. This should be checked by an electrician _immediately_. A bad neutral connection can put up to the full 240V mains supply on what is supposed to be a normal 120V circuit, and in addition to the heating problems mentioned above, could cause expensive electronics to fry even if no significant damage is done to the electrical system.

-Jon
 
  #3  
Old 05-07-04, 10:46 AM
Georgeb
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Thanks for the advice. The house is about 27 years old and the entire sub-division has underground eletrical service which has been quite unreliable. The last time we had a power outage the guy working for the electric company said we should complain about the aging system which continues to break down. Also, we had our kitchen remodeled a couple of months ago and when I mentioned this problem to them, they also said it sounded like a bad feed coming into the house or an improper connection in the box. The main panel is from when the house was built and has really not been changed. This problem has been going on for quite a few years and it has just recently become worse, so I guess it is time for a call to our local electrician.
 
  #4  
Old 05-07-04, 11:25 AM
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Before you call an electrician ($$$), call the power company (free).
 
  #5  
Old 05-07-04, 11:44 AM
Georgeb
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Good idea, thanks. Seeing as how they are probably causing the problem and I'm paying the electric bill every month, might as well get something for it. I still don't understand why it is just the sump pump circuit that causes the lights to flicker that are on different circuits. I just got done mapping all the circuits in my house and found that a couple of circuits need to have some of the load moved to another circuit. I would guess that when the houses in the neighborhood were built they weren't anticipating having all of the recent loads like Microwaves, big screen TV's, Security lights, computers, DVD players...etc being plugged in and being used. Unfortunately I also discovered that I don't have any more room in the main box to add more breakers. Would the power company have to upgrade my service first before having a bigger box installed?
 
  #6  
Old 05-07-04, 01:28 PM
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A physically bigger box (i.e., one with space for more breakers) does not require the power company to upgrade anything. A panel capable of delivering more power, however, may or may not require the power company to do something on their side. Only they can make that call. Whether you just need more circuits or whether you need more power is a complex question.

By the way, the sump pump probably has the biggest inrush current of anything in your house, and is thus most likely to cause a momentary voltage drop. The refrigerator and air conditioner (if you have one) also might do this.
 
  #7  
Old 05-07-04, 05:25 PM
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Originally Posted by John Nelson
Before you call an electrician ($$$), call the power company (free).
Not always free. A buddy in town here called and they told him if the problem was on his side he would be billed for the call. I went and checked out his problem. One hot was dead. They came, pulled the meter and "clipped" it until they could come back in 3 days and fix the underground feeder. No 240 volts but free power for 3 days. His wife was happy too. No stove needed take out every night.
 
  #8  
Old 05-14-04, 12:44 PM
Georgeb
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Well, called the power company and they sent a guy out the same day. He has worked for the company for many years so I think his testing and advice was pretty sound. He checked the power coming in and it looked fine. He checked the hot, neutral and grounds and they also looked fine. Although it was against company policy he actually came inside and checked the box along with checking the drop in voltage when the sump was turned on and found only a slight drop. According to him, he recommed that I balance the load on the different circuits, put the microwave on its own 20amp circuit with 12 gauge. He didn't think it would hurt to try upgrading the sump to a 20amp circuit with 12 gauge. Other than that he said if I wanted to get a bigger box to have more room to expand and balance the loads better, that it wouldn't hurt(Other than my wallet). Also, no need to call them out if I decide to do that. So if moving the sump to a 20amp isn't suppose to make a difference, how can I find out what is causing the problem?
 
  #9  
Old 05-14-04, 12:50 PM
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How long is the sump pump's circuit length from the panel?
 
  #10  
Old 05-14-04, 12:58 PM
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Can you quantify "slight drop"? It only takes a few volts to cause lights to flicker. Maybe your eyes are more sensitive than most. If the flicker is slight, and it doesn't cause your guests to go, "Oh my god, what was that?", then I'd probably just forget it.
 
  #11  
Old 05-17-04, 06:07 AM
Georgeb
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The length between the panel and the sump pump outlet is 12feet. As for the volatage drop it is was about 2-3volts and the flickering is pretty noticable to us and to our kids as well. I also noticed just recently that when our dryer which is a 240 circuit causes a flicker, but only when it first starts. I have a few electircal testing tools and I am wondering if there are a couple of quick/easy tests to prove if the circuits are ok. Otherwise, I think I will switch the sump to the 20amp and 12gauge just to see if that helps. If no difference then I believe it is time for an electrician. Thnks for your help and if anyone has any other suggestions, I'm ready to listen.
 
  #12  
Old 05-17-04, 06:30 AM
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So 2-3 volts is the drop that the power company measured at the service entrance? If so, there's nothing you can do about it.
 
  #13  
Old 05-17-04, 06:51 AM
Georgeb
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The voltage drop was measured at the service entrance. What does that indicate?
 
  #14  
Old 05-17-04, 07:47 AM
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That indicates that the voltage drop is on the utility side. Unless you can talk the utility into upgrading their transformer or wires, you're probably going to have to live with the flicker.
 
  #15  
Old 05-17-04, 07:57 AM
Georgeb
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Thanks for the info. Fat chance that will happen. There has been a huge increase in recidential neighborhoods and businesses within the last few years. I am hoping that they will upgrade their equipment in area as there are many older neighborhoods that are in need of upgrades. We shall see. Nice to know that it isn't something wrong with my electrical panel and system other than needing to balance the loads.
 
  #16  
Old 05-17-04, 08:00 AM
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If the 2-3V is the voltage drop measured at the service entrance, then about the only thing that you can do is try to petition the power company to improve the service drop conductors or the transformer.

It is not clear is the 2-3V drop is the brief voltage drop that you get while the pump is starting, or if it is the voltage drop that you get while it is running. I am presuming that this is the voltage drop _while the pump is starting_ and drawing much more than normal current, but if you are getting a 2-3V drop at your service entrance with a 10A load (my guess for the motor), then you probably have a strong case with your power company that something needs fixing. If you get a 2-3V drop with a 60-100A inrush (again my guess), then you probably don't have a strong case for improved service.

You might consider trying to fund a sump pump motor that operates at 240V but with the same power rating as your present motor. This motor will draw half the current, which means half the voltage drop. It will also spread the voltage drop between both hots in your supply, which will mean that each 120V circuit will only see half of this voltage drop. This will reduce the amount of flicker that you see.

You also might want to search for a pump motor with lower inrush current. I do not know if these are actually available, but I do know that different electric motors have different ratios of startup current to running current, so you may be able to get a motor that has lower startup current.

I would suggest checking with an electric motor repair shop; they may be able to supply a replacement motor that fits your sump pump that meets the desired characteristics (240V, lower inrush)

-Jon
 
  #17  
Old 05-17-04, 08:11 AM
Georgeb
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It's when the pump is starting and I figured it had to be the big draw the motor is using when starting. I really think they are looking at upgrading since when I was talking to my neighbors recently that they too were complaining about similar problems. The guy from the powere company that came out also indicated that we might be in for changes. A couple of big businesses and a new condo neighborhood is coming in and I have seen a lot of surveyors checking things out. We shall see. I don't think I will mess with the pump as it is only a couple of years old and the last one did the same thing. Thanks again though.
 
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